Engine with variable volumetric ratio

A four-stroke internal combustion engine having the following successive phases:

• an intake phase, a compression phase, an expansion phase and an exhaust phase, said engine operating by a combustion selected from the group consisting of self-combustion, controlled ignition and combinations thereof, whereby said engine includes:
• a cylinder housing component having:
• a first series of cylinders, each having an axis and a diameter, and
• a second series of cylinders, each having an axis and diameter,
• whereby the cylinders of the first series having a larger diameter than the diameter of the cylinders of the second series, and whereby the cylinder housing has an upper face along which the cylinders are open,
• a cylinder head part covering at least partly the upper face of the cylinder housing component, said cylinder head part being associated at least with inlet valves and exhaust valves at least for the first series of cylinders,
• a first series of pistons, each piston of said first series being adapted to be driven by an alternative movement in a cylinder of the first series of cylinders along a displacement length, each of said pistons being associated with a connecting rod,
• a second series of pistons, each piston of said second series being adapted to be driven by an alternative movement in a cylinder of the second series of cylinders along a displacement length, each of said pistons being associated with a connecting rod,
• whereby the displacement length of the piston of the cylinder of the first series is larger than the displacement length of the piston of the cylinder of the second series,
• a first crankshaft and a second crankshaft with rotational axes parallel to one another, a first crankshaft having a crank with a large stroke, whilst the second crankshaft has a crank with a small stroke, less than the large stroke of the crank of the first crankshaft, the said crankshafts being adapted to be coupled at the same rotational speed, by means of a gear train and a variably timed transmission;
• at least one variably timed transmission acting on an element selected from the group consisting of the crankshafts, pieces connected to the crankshafts and pieces of the gear train adapted for coupling the crankshafts at the same rotational speed, said variably timed transmission being adapted for adjusting at least a relative angular position between the crankshafts, said relative angular position between the crankshafts being defined by the angle formed between the crank of the first crankshaft and a line parallel to the crank of the second crankshaft and crossing the rotational axis of the first crankshaft;
• in which each piston, being associated with a connecting rod, is operated by a crank of a crankshaft, the crank with the small stroke of the second crankshaft operating the rod of the piston moving within the small cylinder, whilst the crank with the large stroke of the first crankshaft operates the rod of the piston moving within the large cylinder,
• in which the first series of cylinders is laid out above the first crankshaft, whilst the second series of cylinders is laid out above the second crankshaft,
• in which each cylinder of the first series communicates with at least one cylinder of the second series via a clearance space, in such a way as to form a pair of two cylinders communicating with one another to allow the gases to pass from one cylinder to the other, independently of the position of the pistons moving within the said cylinders, and
• in which the upper face of the cylinder housing component is provided with channels forming distinct passages for each pair of cylinders, a channel for one pair of cylinders extending between a cylinder from the first series and a cylinder from the second series, whereby each channel for one pair of cylinders has a mean width determined along the upper face of between 0.5 and 0.8 times the mean of the diameters of the cylinders of the said pair of cylinders.